ESXi 4.x is very, but not completely, similarclick on the image on the right to see a bigger version:

Select the ESXi server in the tree view on the left

Select “Configuration” in the horizontal list of tabs

Select “DNS and routing” in the vertical menu (it is in the “Software” section)

Select “Properties” link on the far up right in your screen

In the dialog it is a bit counter-intuitive:
– Make sure that “Use the following DNS server address” is selected
– Fill in the hostname under “Name”
– Optionally, fillin the “Domain” and “Look for hosts in the following domains”